1. Field of the Invention
The present invention relates to a method for producing a toner to be used as a developer for developing latent electrostatic images in electrophotography, electrostatic recording, electrostatic printing, and the like. The present invention also relates to a toner produced by means of the production method and relates to a toner production apparatus using the method for producing a toner.
2. Description of the Related Art
A developer used in electrophotography, electrostatic recording, electrostatic printing, or the like is once made adhere on an image bearing member, for example, on a latent electrostatic image bearing member with a latent electrostatic image formed thereon in a developing step, then transferred onto a transferring medium such as a transferring paper sheet from the latent electrostatic image bearing member in a transferring step, and then fixed on the paper surface in a fixing step. In the course of the process, as developers used for developing a latent electrostatic image to be formed on the surface of the latent electrostatic image bearing member with the latent image held thereon, there have been known a two-component developer containing a carrier and a toner, and a one-component toner which requires no carrier (magnetic toner, or nonmagnetic toner).
Conventionally, as dry toners used in electrophotography, electrostatic recording, electrostatic printing, and the like, there have been widely used the dry toners that are prepared by dissolving and kneading a toner binder such as styrene resin, and polyester resin along with a colorant or colorants or the like and pulverizing the materials, so-called as pulverized toner.
In recent years, toner production methods by means of suspension polymerization or emulsification aggregation, so-called polymerized toners are studied. Besides, the method accompanying contractions in volume of toner particles, which is referred to as polymer dissolution suspension method, is also studied (see Japanese Patent Application Laid-Open (JP-A) No. 07-152202). The polymer dissolution suspension method is a method of which toner materials are dispersed and dissolved in a volatile solvent such as an organic solvent having a low-boiling point, the dissolved toner solution is emulsified to be made into droplets in an aqueous medium in which a dispersing agent exists, and then the volatile solvent is removed. Unlike suspension polymerization method, and emulsion aggregation method, the polymer dissolution suspension method has high general versatility of usable resins and excels in that polyester resins useful in full-color process particularly requiring transparency and surface smoothness of fixed images can be used.
In the polymerized toner, however, it is based on the assumption that a dispersing agent is used in an aqueous medium. Thus, there are disadvantages known that environment stability is impaired, because a dispersing agent impairing the charge property of toner remains on the toner surface, and that quite a large amount of washing water is required for removing the dispersing agent. Therefore, such a method for producing a polymerized toner leaves something to be desired.
As a method for producing a toner alternative to the toner production method stated above, a method is proposed in which microscopic droplets are formed using a piezoelectric pulse, and the droplets are dried and solidified to thereby produce a toner (see Japanese Patent Application Laid-Open (JP-A) No. 2003-262976. A method is also proposed in which microscopic droplets are formed utilizing effect of thermal expansion within a nozzle, and the droplets are further dried and solidified to thereby produce a toner (see Japanese Patent Application Laid-Open (JP-A) No. 2003-280236). Further, a method is proposed in which a process similar to the above is performed using an acoustic lens (see Japanese Patent Application Laid-Open (JP-A) No. 2003-262977). However, with these methods, there is a problem with poor productivity, because the number of droplets per unit time of the droplets that can be ejected from a nozzle is small, and it is impossible to avoid widening the particle size distribution caused by coalescence of droplets, and thus it is unsatisfactory in monodispersity.